Private branch exchange (PBX) systems are well known in the art. In a typical arrangement, an enterprise will operate a PBX server that interfaces between each of the telephone stations in the enterprise and a local telephone company central office of the public switched telephone network (PSTN). Conventionally, each telephone station will have an assigned PBX extension number, and some of the stations may also have direct inbound dial (DID) numbers for receiving calls directly from the PSTN. The PBX server may then provide its stations with many useful features, such as the ability to dial by extension, the ability to transfer calls, the ability to establish conference calls, and the ability to interact with an enterprise voice mail service.
Traditional PBX servers connect with each of their served telephone stations by a respective physical telephone line, which can be inefficient and difficult to manage. Recent improvements in Voice-over-IP communications have made possible an improved form of PBX server, known generally as an IP PBX server. Typically, an IP PBX server sits as a node on an enterprise's computer network (e.g., LAN), and each of the enterprise telephone stations in turn sits as a respective node on the computer network as well. Signaling and bearer communications between the telephone stations and the IP PBX server then traverse the computer network as IP communications. Like a conventional PBX server, the IP PBX server may be coupled to a telephone company central office, so that the enterprise telephone stations can place and receive calls via the PSTN.
An enterprise IP PBX system provides great convenience for users of desktop telephone stations at the enterprise. Increasingly, however, people are often working from home or otherwise on the road, rather than at the office. As such, people frequently use cellular wireless communication devices (WCDs), such as cell phones, rather than their desktop enterprise telephone stations. WCDs place and receive calls through cellular radio access networks, rather than through an IP PBX system. Thus, when on the road, an enterprise worker would not benefit from the features of the enterprise IP PBX system (other than by dialing into the IP PBX system through a DID telephone number.)